RESUMEN
The quantity and composition of rice proteins play a crucial role in determining taste quality of sake, Japanese rice wine. However, the spatial distribution of proteins within rice grains, especially in endosperm tissue, and the differences between rice varieties remain unclear. Here, we analyzed the crude protein contents and composition ratios of table (Nipponbare and Koshihikari) and genuine sake rice varieties (Yamadanishiki, Gohyakumangoku, Dewasansan, Dewanosato, and Yumenokaori) to elucidate their spatial distribution within the Japonica rice grain endosperm. Seven sake rice varieties were polished over five harvest years using a brewer's rice-polishing machine. We obtained fractions at 90-70% (the outermost endosperm fraction), 70-50%, 50-30%, and 30-0% (the central region of the endosperm fraction). Yamadanishiki and Dewanosato exhibited considerably lower crude protein contents than the other cultivars. After applying SDS-PAGE, the protein composition, comprising glutelin/total protein (G/TP), prolamin/TP (P/TP), and G/P ratios of these fractions was determined. In white rice (at a 90% rice-polishing ratio), the average ratio of the major protein composition was G/TP 41%, P/TP 21%, and G/P ratios of 1.97. Gohyakumangoku and Yamadanishiki had higher G/TP ratio, while Dewanosato had a lower value. Despite having lower crude protein contents, Yamadanishiki and Dewanosato exhibited significantly varying G/TP ratios. The G/TP ratio markedly varied among rice varieties, particularly in the rice grains' central region. The 50-30% fraction had the highest P/TP ratio among all tested rice varieties, suggesting spatial differences in P/TP within rice grains. Koshihikari had the lowest P/TP ratio. In addition, the 50-30% fraction had the lowest G/P ratio among all tested rice varieties, with Gohyakumangoku having the highest G/P ratio. Dewanosato had the lowest G/P value, and this value significantly differed from that of Yamadanishiki in the 30-0% fraction. We found substantial differences in protein composition within distinct spatial regions of rice grains, and larger differences among rice varieties were observed in the rice grain's central region.
RESUMEN
Hakutsurunishiki is a sake rice cultivar bred using Yamadabo (seed parent) and Wataribune 2 (pollen parent), equivalent to a Yamadanishiki sibling. This study evaluated the structural characteristics of the Hakutsurunishiki rice grain that contribute to the brewing characteristics of daiginjo-shu, via a comparison with Yamadanishiki. Hakutsurunishiki brown rice was a little heavy and had a large white core. Observing a cross-section of white rice after soaking revealed that the rice grain structure of Hakutsurunishiki was different from that of Yamadanishiki. Hakutsurunishiki white rice showed fewer voids than Yamadanishiki, promoting a slower water absorption rate. Glucose distribution in rice koji obtained by mass spectrometry imaging showed that Hakutsurunishiki rice koji, like Yamadanishiki, is tsuki-haze type, suggesting that its grain structure is suitable for making rice koji for daiginjo-shu. With these observations, we were able to clarify the structural characteristics of Hakutsurunishiki rice grain.
Asunto(s)
Bebidas Alcohólicas , Oryza , Bebidas Alcohólicas/análisis , Oryza/química , Fitomejoramiento , Grano Comestible/química , Agua , FermentaciónRESUMEN
The stable isotopic compositions of carbon (δ13C) and oxygen (δ18O) in rice are often used to confirm its authenticity. The gelatinization temperature is a crucial factor in alcoholic fermentation. However, little is known about the isotopic and thermal responses of rice to climate change. We show that in sake rice grown annually in the same paddy field from 1994 to 2013, the δ13C (-27.4 to -25.9) and δ18O values (20.4 to 27.0) correlated negatively with the mean daily minimum air temperature and precipitation, and positively with the hours of sunshine during grain-filling. In contrast, of the air temperatures tested, the gelatinization temperature of the rice grains (63.2°C to 70.0 °C) correlated positively and most strongly with the mean daily mean air temperature. Thus, we identified the mean daily minimum temperature during grain-filling, a nocturnal temperature, as a major factor affecting the isotopic and thermal variations in rice grains.
Asunto(s)
Isótopos de Carbono/análisis , Oryza/química , Oryza/crecimiento & desarrollo , Isótopos de Oxígeno/análisis , Cambio Climático , Gelatina/química , Japón , Luz Solar , TemperaturaRESUMEN
Sake-brewing cultivars among varieties of Japanese rice (Oryza sativa L.) have traits adapted to the sake-brewing process, such as a high white-core expression rate (WCE). Our previous study detected putative quantitative trait loci (QTLs) associated with a high WCE derived from Yamadanishiki, a popular brewing rice cultivar. Because the occurrence of white-core grains depends on air temperature and the position of the grain on the panicle, phenotyping of WCE must consider these variable conditions. In this study, qWCE6, a QTL for the WCE on chromosome 6, was validated for the first time, and the phenotyping method examined for its suitability in fine-mapping. A clear tendency towards high WCE was observed in late-heading substituted lines which headed under low daily mean temperature at the experimental location. White-core grains were often expressed by the primary spikelets on the upper panicle, producing a high percentage of superior grains. The segregating population for qWCE6 in late heading revealed a distinct difference in WCE between the Koshihikari and Yamadanishiki homozygous alleles at qWCE6 as determined from that locality. Further, two insertion/deletion markers were developed for the marker-assisted selection of qWCE6. Our results will be useful for informing the breeding of sake-brewing rice cultivars.
RESUMEN
KEY MESSAGE: GluA and GluB-4/5 glutelin subfamilies are mainly localized to outer region of the endosperm, particularly in its ventral side, in rice grain, but GluC is localized to throughout the endosperm. The major seed storage protein in rice (Oryza sativa) is glutelin, which forms a vacuole-derived protein body type-II. Glutelins are encoded by multiple genes, and generally comprise four protein subfamilies, namely, GluA, GluB, GluC, and GluD: however, the localization pattern of glutelin in rice grains remains obscure. In this study, we investigated the localization pattern of five subtypes of the glutelin protein in rice grains using glutelin-subtype specific antibodies. Immunoblot analysis against sequentially polished rice flour fractions from three crop years and seven japonica rice varieties revealed that GluA was strongly localized in the outer region of the endosperm, including the subaleurone layer, whereas GluC was distributed throughout the endosperm. Among the glutelin subtypes, GluA was mostly found in the outer region of the rice grain, followed by GluB-4/5, GluB-1, GluD, and GluC. Immunofluorescence labeling microscopy analysis using immature rice seeds clearly revealed that the localization pattern of GluC and GluD was completely different from that of GluA and GluB. Expression levels of all glutelins, particularly GluA, GluB-1, and GluB-4/5, were stronger on the ventral than dorsal side in rice grains. These results provide strong and consistent evidence that glutelins localize to the rice grain in a subfamily-dependent manner.